Modulation method and apparatus

ABSTRACT

Embodiments of this application provide a modulation method and apparatus. The method includes: receiving a code word sequence, where each code word includes N bits, and the code word sequence includes at least a first code word; mapping the code word sequence into M sequences, where each sequence includes N/M bits from the first code word; mapping the M sequences into a symbol sequence, where each symbol is corresponding to M bits, the M bits are respectively from the M sequences, first bits corresponding to N/M first-type symbols are from the first code word, and second bits corresponding to N/M second-type symbols are from the first code word. Thus a signal-to-noise ratio requirement during higher order modulation lowered.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/CN2017/071926, filed on Jan. 20, 2017, which claims priority to Chinese Patent Application No. 201610143878.X, filed on Mar. 14, 2016. The disclosures of the aforementioned applications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

This application relates to the field of communications technologies, and in particular, to a modulation method and apparatus.

BACKGROUND

With development of communications technologies, a transmission rate required by a communications system increases exponentially. Because communication spectrum resources are increasingly scarce, spectrum utilization of a system needs to be fully improved. Manners are studied to improve spectrum efficiency of various communications systems, for example, a microwave backhaul system, a copper wire system, a satellite communication system, a wireless communications system, and a fiber-optic communications system.

Higher order modulation is the first approach used to develop high spectrum efficiency in a communications system. Although the system spectrum efficiency can be greatly improved by using the higher order modulation, the system is required to provide a larger signal-to-noise ratio (SNR). In other words, with a same SNR, a higher modulation order indicates a higher system bit error rate.

SUMMARY

Embodiments of this application disclose a modulation method and apparatus, so as to resolve a problem that a larger signal-to-noise ratio needs to be provided for higher order modulation.

According to a first aspect, an embodiment of this application provides a modulation method, and the method may be implemented by using a modulator on a transmit end. The modulator is configured to modulate a code word into a symbol. The modulator first receives a code word sequence, where each code word includes N bits, and the code word sequence includes at least a first code word; then maps the code word sequence into M sequences, where each sequence includes N/M bits from the first code word; and finally maps the M sequences into a symbol sequence, where each symbol is corresponding to M bits, the M bits are respectively from the M sequences, first bits corresponding to N/M first-type symbols are from the first code word, and second bits corresponding to N/M second-type symbols are from the first code word. Each sequence includes N/M bits from the first code word. Therefore, a first bit corresponding to the second-type symbol is definitely from another code word different from the first code word. Therefore, a bit in the second-type symbol and from the another code word may be demodulated by using information about the first code word, so that the bit in the second-type symbol and from the another code word can be demodulated more accurately, thereby lowering a signal-to-noise ratio requirement during higher order modulation.

In a possible design, the symbol is corresponding to one constellation point in 2^(m) constellation points in a 2^(m) constellation diagram, a minimum Euclidean distance between the constellation points in the 2^(m) constellation diagram is a first Euclidean distance, a minimum Euclidean distance between constellation points that are in the 2^(m) constellation diagram and that may be corresponding to the first-type symbols after bits from the first code word are determined is a second Euclidean distance, and the second Euclidean distance is greater than the first Euclidean distance. The minimum Euclidean distance between the possible constellation points obtained after the bits from the first code word are determined increases. Therefore, demodulation is more accurate, so as to better lower the signal-to-noise ratio requirement during higher order modulation.

In another possible design, the mapping the code word sequence into M sequences may include: performing serial-to-parallel conversion on the code word sequence to obtain the M sequences, where each sequence includes N/M bits from the first code word; and performing delay processing on at least one sequence in the M sequences, where a quantity of delayed bits is X*(N/M), and X is an integer greater than or equal to 1. A solution that is implemented by using a serial-to-parallel converter and a delayer is simple and easy to implement.

In another possible design, the mapping the code word sequence into M sequences includes: interleaving the code word sequence to obtain the M sequences, where each sequence includes N/M bits from the first code word. In a solution that is implemented by using an interleaver, an interleaving rule of the interleaver needs to be designed. A requirement for a designer is relatively high, but system costs may be reduced.

In another possible design, when M is 3, the mapping the code word sequence into M sequences specifically includes: performing serial-to-parallel conversion on the code word sequence to obtain three sequences, where each sequence includes N/3 bits from the first code word; and performing delay processing on a first sequence, where a quantity of delayed bits is N/3.

In another possible design, when M is 3, the mapping the code word sequence into M sequences specifically includes: performing serial-to-parallel conversion on the code word sequence to obtain three sequences, where each sequence includes N/3 bits from the first code word; performing delay processing on a first sequence, where a quantity of delayed bits is N/3; and performing delay processing on a second sequence, where a quantity of delayed bits is N/3.

In another possible design, when M is 3, the mapping the code word sequence into M sequences specifically includes: performing serial-to-parallel conversion on the code word sequence to obtain three sequences, where each sequence includes N/3 bits from the first code word; performing delay processing on a first sequence, where a quantity of delayed bits is 2(N/3); and performing delay processing on a second sequence, where a quantity of delayed bits is N/3.

According to a second aspect, an embodiment of this application provides a receiving method. The receiving method is used by a demodulator on a receive end to receive a symbol sequence generated by using the modulation method provided in the first aspect. The receiving method includes: first, receiving a symbol sequence transmitted by using a channel; demodulating a first-type symbol to obtain a log-likelihood ratio of a bit from a first code word; demodulating a second-type symbol to obtain a log-likelihood ratio of a bit from the first code word; performing decoding based on log-likelihood ratios of all bits from the first code word to obtain first extrinsic information; and demodulating the second-type symbol by using the first extrinsic information to obtain a log-likelihood ratio of a bit from another code word. The second-type symbol may be demodulated by using first extrinsic information related to the first code word, so that a bit in the second-type symbol and from another code word can be demodulated more accurately.

In a possible design, the first-type symbol further includes a bit from a second code word, and before the demodulating a first-type symbol to obtain a log-likelihood ratio of a bit from a first code word, the method further includes: performing decoding based on log-likelihood ratios of all bits from the second code word to obtain second extrinsic information; and the demodulating a first-type symbol to obtain a log-likelihood ratio of a bit from a first code word includes: demodulating the first-type symbol by using the second extrinsic information to obtain the log-likelihood ratio of the bit from first code word.

In a possible design, the first extrinsic information is information obtained after prior information of the decoding is subtracted from posterior information that is obtained after the decoding; or the first extrinsic information is posterior information that is obtained after the decoding.

According to a third aspect, an embodiment of this application provides a modulation apparatus such as a modulator. The modulation apparatus includes: a first mapper, configured to: receive a code word sequence, where each code word includes N bits, and the code word sequence includes at least a first code word; and map the code word sequence into M sequences, where each sequence includes N/M bits from the first code word; and a second mapper, configured to map the M sequences into a symbol sequence, where each symbol is corresponding to M bits, the M bits are respectively from the M sequences, first bits corresponding to N/M first-type symbols are from the first code word, and second bits corresponding to N/M second-type symbols are from the first code word.

In a possible design, the symbol is corresponding to one constellation point in 2^(m) constellation points in a 2^(m) constellation diagram, a minimum Euclidean distance between the constellation points in the 2^(m) constellation diagram is a first Euclidean distance, a minimum Euclidean distance between constellation points that are in the 2^(m) constellation diagram and that may be corresponding to the first-type symbols after bits from the first code word are determined is a second Euclidean distance, and the second Euclidean distance is greater than the first Euclidean distance.

In a possible design, the first mapper includes a serial-to-parallel converter and a delayer, where the serial-to-parallel converter is configured to: receive a code word sequence, where each code word includes N bits, and the code word sequence includes at least a first code word; and perform serial-to-parallel conversion on the code word sequence to obtain M sequences, where each sequence includes N/M bits from the first code word; and the delayer is configured to perform delay processing on at least one sequence in the M sequences, where a quantity of delayed bits is X*(N/M), and X is an integer greater than or equal to 1.

In a possible design, the first mapper includes an interleaver, where the interleaver is configured to: receive a code word sequence, where each code word includes N bits, and the code word sequence includes at least a first code word; and interleave the code word sequence to obtain M sequences, where each sequence includes N/M bits from the first code word.

In a possible design, the first mapper includes a serial-to-parallel converter and a delayer, where the serial-to-parallel converter is configured to: receive a code word sequence, where each code word includes N bits, and the code word sequence includes at least a first code word; and perform serial-to-parallel conversion on the code word sequence to obtain three sequences, where each sequence includes N/3 bits from the first code word; and the delayer is configured to perform delay processing on a first sequence, where a quantity of delayed bits is N/3.

In a possible design, the first mapper includes a serial-to-parallel converter and a delayer, where the serial-to-parallel converter is configured to: receive a code word sequence, where each code word includes N bits, and the code word sequence includes at least a first code word; and perform serial-to-parallel conversion on the code word sequence to obtain three sequences, where each sequence includes N/3 bits from the first code word; and the delayer is configured to: perform delay processing on a first sequence, where a quantity of delayed bits is N/3; and perform delay processing on a second sequence, where a quantity of delayed bits is N/3.

In a possible design, the first mapper includes a serial-to-parallel converter and a delayer, where the serial-to-parallel converter is configured to: receive a code word sequence, where each code word includes N bits, and the code word sequence includes at least a first code word; and perform serial-to-parallel conversion on the code word sequence to obtain three sequences, where each sequence includes N/3 bits from the first code word; and the delayer is configured to: perform delay processing on a first sequence, where a quantity of delayed bits is 2(N/3); and perform delay processing on a second sequence, where a quantity of delayed bits is N/3.

According to a fourth aspect, an embodiment of this application provides a receiving apparatus, including: a demodulator, configured to receive a symbol sequence transmitted by using a channel, where the symbol sequence is a symbol sequence generated in any one of claims 11 to 17; demodulate a first-type symbol to obtain a log-likelihood ratio of a bit from a first code word; and demodulate a second-type symbol to obtain a log-likelihood ratio of a bit from the first code word; and a decoder, configured to perform decoding based on log-likelihood ratios of all bits from the first code word to obtain first extrinsic information; where, in addition to receiving the symbol sequence transmitted by using the channel, the demodulator is further configured to demodulate the second-type symbol by using the first extrinsic information to obtain a log-likelihood ratio of a bit from another code word.

In a possible design, the first-type symbol further includes a bit from a second code word; the decoder is further configured to perform decoding based on log-likelihood ratios of all bits from the second code word to obtain second extrinsic information; and that the demodulator is configured to demodulate the first-type symbol to obtain the log-likelihood ratio of the bit from the first code word includes: the demodulator is configured to demodulate the first-type symbol by using the second extrinsic information to obtain the log-likelihood ratio of the bit from first code word.

In a possible design, the first extrinsic information is information obtained after prior information of the decoding is subtracted from posterior information that is obtained after the decoding; or the first extrinsic information is posterior information that is obtained after the decoding.

In the modulation method provided in the embodiments of this application, each sequence in the M sequences includes the N/M bits from the first code word, the first bits corresponding to the N/M first-type symbols in the symbol sequence are from the first code word, and the second bits corresponding to the N/M second-type symbols in the symbol sequence are from the first code word. As a result, a first bit corresponding to the second-type symbol is definitely from another code word different from the first code word. Therefore, a bit in the second-type symbol and from the another code word may be demodulated by using information about the first code word, so that the bit in the second-type symbol and from the another code word can be demodulated more accurately, thereby lowering a signal-to-noise ratio requirement during higher order modulation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a structural diagram of an information sending network according to an embodiment of this application;

FIG. 1B is a constellation diagram according to an embodiment of this application;

FIG. 2A is a structural diagram of a transmit end device according to an embodiment of this application;

FIG. 2B is a structural diagram of another transmit end device according to an embodiment of this application;

FIG. 2C is a structural diagram of still another transmit end device according to an embodiment of this application;

FIG. 2D is a structural diagram of still another transmit end device according to an embodiment of this application;

FIG. 2E is a structural diagram of still another transmit end device according to an embodiment of this application;

FIG. 3A is a schematic diagram of an input bit stream of a mapper according to an embodiment of this application;

FIG. 3B is a schematic diagram of an input bit stream of another mapper according to an embodiment of this application;

FIG. 3C is a schematic diagram of an input bit stream of still another mapper according to an embodiment of this application;

FIG. 3D is a schematic diagram of an input bit stream of still another mapper according to an embodiment of this application;

FIG. 4A is an 8QAM constellation diagram according to an embodiment of this application;

FIG. 4B is another 8QAM constellation diagram according to an embodiment of this application;

FIG. 5A is a structural diagram of a receive end device according to an embodiment of this application;

FIG. 5B is a structural diagram of another receive end device according to an embodiment of this application;

FIG. 6A and FIG. 6B are a processing flowchart of a receive end device according to an embodiment of this application;

FIG. 7A is a schematic diagram of parameter configuration of NUM_(i) when m=4 according to an embodiment of this application;

FIG. 7B is a schematic diagram of parameter configuration of NUM_(i) when m=5 according to an embodiment of this application;

FIG. 7C is a schematic diagram of parameter configuration of NUM_(i) when m=6 according to an embodiment of this application;

FIG. 7D is a schematic diagram of parameter configuration of NUM_(i) when m=7 according to an embodiment of this application;

FIG. 7E is a schematic diagram of parameter configuration of NUM_(i) when m=8 according to an embodiment of this application;

FIG. 7F is a schematic diagram of parameter configuration of NUM_(i) when m=9 according to an embodiment of this application;

FIG. 7G is a schematic diagram of parameter configuration of NUM_(i) when m=10 according to an embodiment of this application;

FIG. 7H is a schematic diagram of parameter configuration of NUM_(i) when m=11 according to an embodiment of this application; and

FIG. 7I is a schematic diagram of parameter configuration of NUM_(i) when m=12 according to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

The following describes the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application.

The embodiments of this application have wide application scenarios, for example, a microwave backhaul system, a copper wire system, a satellite communication system, a wireless communications system, and a fiber-optic communications system. The embodiments of this application are mainly applied to information transmission between devices. FIG. 1A is a structural diagram of a typical information sending network. The network includes a transmit end device 101 and a receive end device 102. A link 103 between the transmit end device 101 and the receive end device 102 may be a microwave link, a copper link, a satellite link, a wireless communications link, a fiber link, and the like. The transmit end device 101 sends a signal to the receive end device 102. Before sending the signal, the transmit end device 101 needs to perform processing such as coding and modulation on a to-be-sent information bit.

For ease of the following description, several concepts are first described.

Information bit stream: U={{u_(1,1), u_(1,2), . . . , u_(1,k)}, {u_(2,1), u_(2,2), . . . , u_(2,k)}, {u_(3,1), u_(3,2), . . . , u_(3,k)}, . . . }, where {u_(1,1), u_(1,2), . . . , u_(1,k)} is an information sequence.

Coding: Coding in the embodiments of this application is channel coding, and is essentially to improve communication reliability and reduce a bit error rate of transmission. A channel coding process includes inserting some redundant bits into a source data bit stream with a specific length, so as to check and correct an error in source data bits at a receive end by using a relationship between the redundant bits and the source data bits, thereby achieving an objective of error correction. Generally, the source data bit is referred to as an information bit, and the redundant bit is referred to as a check bit. For example, the information bit stream U={{u_(1,1), u_(1,2), . . . , u_(1,k)}, {u_(2,1), u_(2,2), . . . , u_(2,k)}, {u_(3,1), u_(3,2), . . . , u_(3,k)}, . . . } enters a coder, and every k bits form one information sequence denoted as U_(i). Each information sequence is coded by using a same coding rule, and p check bits are added into each information sub-sequence to form a code word whose length is n. A coded bit stream Q={{q_(1,1), q_(1,2), . . . , q_(1,n)}, {q_(2,1), q_(2,2), . . . , q_(2,n)}, {q_(3,1), q_(3,2), . . . , q_(3,n)}, . . . } is output, where {q_(i,1), q_(i,2), . . . , q_(i,n)} is referred to as one code word and denoted as Q_(i).

Code word: After coding processing, a code word such as the code word Q_(i)={q_(i,1), q_(i,2), . . . , q_(i,n)} mentioned above may be obtained. A length of Q_(i) is n, that is, Q_(i) includes n bits, and the n bits meet a check relationship. In some scenarios, these code words may be processed to obtain a new code word. For example, a new code word is generated by shortening or puncturing the n bits that meet the check relationship; a new cord word is generated by padding a known bit into the n bits that meet the check relationship; a new code word is obtained by combining a plurality of code words; and a new code word is obtained by interleaving the n bits that meet the check relationship.

Modulation: A 2^(m)QAM modulator maps m input bit streams into one symbol stream. In a 2^(m)QAM modulation scheme, there are in total 2^(m) modulation symbols {s^(j), s², . . . , s² ^(m) } corresponding to 2^(m) complex number constellation points in a modulation constellation diagram. Each complex number constellation point includes an I component and a Q component, and each modulation symbol s^(j) is mapped from m bits (b₁, b₂, . . . b_(m)). For example, for an 8QAM modulator, there are in total eight constellation points in a constellation diagram, which are corresponding to eight modulation symbols. As shown in an 8QAM constellation diagram in FIG. 1B, each symbol is mapped from three bits, and a mapping relationship between bits and symbols is shown in Table 1. A plurality of solutions may be used to modulate a symbol onto a carrier. For example, amplitude modulation may be performed on an I component and a Q component of each symbol, and the I component and the Q component are correspondingly modulated on two mutually orthogonal carriers respectively for sending. The carriers herein may be electrical carriers, optical carriers, and the like.

TABLE 1 Mapping relationship between symbols and bits in 8QAM Bits I Q 000 −1 −1 001 3 −1 011 1 −3 010 −3 −3 110 −1 3 111 3 3 101 1 1 100 −3 1

A to-be-modulated code word sequence is processed in the embodiments of this application, so that a specific correspondence exists between a modulation symbol and a to-be-modulated code word. Specifically, each code word in the to-be-modulated code word sequence includes N bits, and the to-be-modulated code word sequence includes at least a first code word. The code word sequence is mapped into M sequences, where each sequence includes N/M bits from the first code word. The M sequences are mapped into a symbol sequence, where each symbol is corresponding to M bits, the M bits are respectively from the M sequences, first bits corresponding to N/M first-type symbols are from the first code word, and second bits corresponding to N/M second-type symbols are from the first code word.

To compensate for an SNR cost brought by higher order modulation, this application provides a method for coding and mapping a modulated bit, so that bits mapped into a same higher order modulation symbol are from two or more code words. In this way, during demodulation, more accurate information is obtained after decoding is completed by using a bit from a previous code word, so as to help demodulate a bit from a second code word. The second code word is decoded by using a demodulated bit from the second code word to obtain accurate information, so as to help demodulate a bit from a third code word. By analogy, demodulation of all bits is completed.

The following uses 8QAM modulation as an example for description. There are in total eight constellation points in an 8QAM constellation diagram, which are corresponding to eight modulation symbols. Each modulation symbol is mapped from three bits.

As shown in FIG. 2A, FIG. 2A is a structural diagram of a transmit end device according to an embodiment of this application. The transmit end device includes: a coder 201, an interleaver 202, and a modulator 203.

The coder 201 is configured to implement the coding function mentioned above. For example, the information bit stream U={{u_(1,1), u_(1,2), . . . , u_(1,k)}, {u_(2,1), u_(2,2), . . . , u_(2,k)}, {u_(3,1), u_(3,2), . . . , u_(3,k)}, . . . } enters the coder, and every k bits form one information sequence denoted as U_(i). Each information sequence is coded by using a same coding rule, and p check bits are added into each information sub-sequence to form a code word whose length is n. A coded bit stream Q={{q_(1,1), q_(1,2), . . . , q_(1,n)}, {q_(2,1), q_(2,2), . . . , q_(2,n)}, {q_(3,1), q_(3,2), . . . , q_(3,n)}, . . . } is output, where {q_(i,1), q_(i,2), . . . , q_(i,n)} is referred to as one code word and denoted as Q_(i).

The interleaver 202 may perform bit-level interleaving processing on the coded bit stream output by the coder 201, and output an interleaved coded bit stream that may be denoted, for example, as A={{A_(1,1), A_(1,2), . . . , A_(1,n)}, {A_(2,1), A_(2,2), . . . , A_(2,n)}, {A_(3,1), A_(3,2), . . . , A_(3,n)}, . . . }. A_(i)={A_(1,1), A_(1,2), . . . , A_(1,n)} is denoted as one interleaved code word. Certainly, a length of the interleaved code word may be different from a length of the code word before the interleaving. In this embodiment of this application, the interleaver 202 is optional, and the coded bit stream output by the coder 201 may be directly sent to the modulator 203.

The modulator 203 includes a serial-to-parallel converter 2031, a delayer 2032, and a mapper 2033.

The serial-to-parallel converter 2031 performs serial-to-parallel convention on the interleaved coded bit stream to convert the interleaved coded bit stream into three sequences, where each code word A_(i)={A_(i,1), A_(i,2), . . . , A_(i,n)} is equally divided into three parts. If the code word A_(i)={A_(i,1), A_(i,2), . . . , A_(i,n)} cannot be equally divided, the code word may be processed before serial-to-parallel conversion to obtain a new code word, and the new code word can be equally divided into three parts. For example, the new code word may be generated by shortening or puncturing the code word A_(i)={A_(i,1), A_(i,2), . . . , A_(i,n)}; the new code word may be generated by padding a known bit into the code word A_(i)={A_(i,1), A_(i,2), . . . , A_(i,n)}; or the new code word may be obtained by combining a plurality of code words A_(i)={A_(i,1), A_(i,2), . . . , A_(i,n)}. Certainly, if there is no interleaver 202, the modulator receives the coded bit stream from the coder 201, and Q_(i)={q_(i,1), q_(i,2), . . . , q_(i,n)} may be processed to obtain the new code word.

Serial-to-parallel conversion may be performed on A={{A_(1,1), A_(1,2), . . . , A_(1,n)}, {A_(2,1), A_(2,2), . . . , A_(2,n)}, {A_(3,1), A_(3,2), . . . , A_(3,n)}, . . . } in a unit of bit. For example, A_(1,1) is in a first sequence, A_(1,1) and A_(1,2) are in a second sequence, and so on. Alternatively, serial-to-parallel conversion may be performed in a unit of n/m bits. For example, A_(1,1), A_(1,2), . . . , A_(1,n/m) are in a first sequence, and A_(1,(n/m)+1), A_(1,(n/m)+2), . . . , A_(1,2(n/m)) are in a second sequence. Certainly, another conversion method may also be used, and bits of the code word A₁ and bits of the code word A₂ may even alternately appear in one sequence, provided that one code word is equally divided into n/m parts. In this embodiment, one code word only needs to be equally divided into n/3 parts.

As shown in FIG. 2A, the first sequence in this embodiment of this application includes n/3 delayers 3032 marked as T, and a quantity of delayed bits is n/3. Certainly, in another embodiment, the second sequence or the third sequence may include n/3 delayers 3032.

The mapper 2033 is configured to map three input bit sequences into a symbol sequence S. For ease of description, every three parallel bits in the three input bit sequences are referred to as one modulation sequence, and each modulation sequence may be mapped into one symbol.

An input bit stream of the mapper 2033 is shown in FIG. 3A. X represents 0 or 1 and may be set by a user, and A_(i) indicates that a bit is from a code word A_(i). For example, in an n^(th) modulation sequence shown in a dashed circle, d_(1,n) is from a code word A₂, and other bits d_(2,n) and d_(3,n) are from a code word A₃. That is, input bits corresponding to the n^(th) modulation sequence are separately from the code word A₂ and the code word A₃, provided that first bits corresponding to n/3 first-type symbols are from the first code word, and second bits corresponding to n/3 second-type symbols are also from the first code word. For example, as shown in FIG. 3A,

$\frac{n}{3}$ symbols from the first symbol to a

$\frac{n^{th}}{3}$ symbol are first-type symbols, and second bits corresponding to the

$\frac{n}{3}$ symbols are from the code word A₁; and

$\frac{n}{3}$ symbols from a

$\left( {\frac{n}{3} + 1} \right)^{th}$ symbol to a

$\frac{2n^{th}}{3}$ symbol are second-type symbols, and first bits corresponding to the

$\frac{n}{3}$ symbols are also from the code word A₁.

As shown in FIG. 2B, FIG. 2B is a structural diagram of a transmit end device according to an embodiment of this application. A difference between FIG. 2B and FIG. 2A is that a second sequence in FIG. 2B also includes n/3 delayers 3032.

An input bit stream of the mapper 2033 is shown in FIG. 3B. X represents 0 or 1 and may be set by a user, A_(i) indicates that a bit is from a code word A_(i), and d_(i,j) indicates a bit that is of a bit stream D_(i) and that is input into a modulation sequence j. For example, in an n^(th) modulation sequence shown in a dashed circle, d_(1,n) and d_(2,n) are from a code word A₂, and a bit d_(3,n) is from a code word A₃, that is, input bits corresponding to the n^(th) modulation sequence are separately from the code word A₂ and the code word A₃.

As shown in FIG. 2C, FIG. 2C is a structural diagram of a transmit end device according to an embodiment of this application. A difference between FIG. 2C and FIG. 2B is that a first sequence in FIG. 2C includes 2(n/3) delayers 3032.

An input bit stream of the mapper 2033 is shown in FIG. 3C. X represents 0 or 1 and may be set by a user, A_(i) indicates that a bit is from a code word A_(i), and d_(i,j) indicates a bit that is of a bit stream D_(i) and that is input into a modulation sequence j. For example, in an n^(th) modulation sequence shown in a dashed circle, d_(1,n) is from a code word A₁, d_(2,n) is from a code word A₂, and d_(3,n) is from a code word A₃, that is, input bits corresponding to the n^(th) modulation sequence are separately from the code word A₁, the code word A₂, and the code word A₃.

In another embodiment, another modulation scheme different from the 8QAM modulation may be used. For 2^(m)QAM modulation, m may be another value that is at least 3.

As shown in FIG. 2D, FIG. 2D is a structural diagram of a transmit end device according to an embodiment of this application, and main differences between FIG. 2D and FIG. 2A are as follows:

A serial-to-parallel converter 2031 in FIG. 2D directly receives a coded bit stream from a coder 201, and the coded bit stream may be, for example, Q={{q_(1,1), q_(1,2), . . . , q_(1,n)}, {q_(2,1), q_(2,2), . . . , q_(2,n)}, {q_(3,1), q_(3,2), . . . , q_(3,n)}, . . . }.

The serial-to-parallel converter 2031 in FIG. 2D performs serial-to-parallel conversion on the receive coded bit stream to convert the coded bit stream into m sequences. Each code word Q_(i)={q_(i,1), q_(i,2), . . . , q_(i,n)} is equally divided into m parts respectively corresponding to m sequences.

As shown in FIG. 2D, there are NUM_(i) sequences each of which includes x_(i)*(n/m) delayers 3032, where NUM_(i) is an integer greater than or equal to 1, x_(i) is an integer greater than or equal to 0. For example, there are NUM₁, sequences each of which includes x₁*(n/m) delayers 3032, NUM₂ sequences each of which includes x₂*(n/m) delayers 3032, and NUM_(z) sequences each of which includes x_(z)*(n/m) delayers 3032. Preferably, x_(i)>x_(i)+1 may be set.

The mapper 2033 in FIG. 2D is configured to map m input bit sequences into a symbol sequence. For ease of description, every m parallel bits in the m input bit sequences are referred to as one modulation sequence, and each modulation sequence may be mapped into one symbol s^(j). In the 2^(m)QAM modulation, there are in total 2^(m) modulation symbols {s^(j), s², . . . , s² ^(m) }, and each modulation symbol^(j) is mapped from m bits (b¹, b², . . . b^(m)).

An input bit stream of the mapper 2033 is shown in FIG. 3D. X represents 0 or 1 and may be set by a user, and A_(i) indicates that a bit is from a code word A_(i). For example, for a (x₁+1)*(n/m)^(th) modulation sequence shown in a dashed circle, d_(1,(x1+1)*(n/m)), d_(2,(x1+1)*(n/m)), . . . , and d_(NUM1,(x1+1)*(n/m)) are from a code word A₁; d_(NUM1+1,(x1+1)*(n/m)), d_(NUM1+2,x1*(n/m)), . . . , and d_(NUM1+NUM2,x1*(n/m)) are from a code word A₂; and d_(m-NUMZ+1,(x1+1)*(n/m)), d_(m-Numz+2,(x1+1)*(n/m)), . . . , and d_(m,(x1+1)*(n/m)) are from a code word A_(z). That is, input bits corresponding to the (x₁+1)*(n/m)^(th) modulation sequence are separately from A₁, A₂, . . . , and A_(z). That is, the bits corresponding to the (x₁+1)*(n/m)^(th) modulation sequence are from Z code words, that is, the bits include NUM₁, NUM₂, . . . , and NUM_(Z) that are respectively extracted from the Z code words A₁, A₂, . . . , and A_(z). NUM_(i) is an integer that is greater than or equal to 1 and less than or equal to m, Z is an integer that is greater than 1 but less than or equal to m, and

${\sum\limits_{i = 1}^{Z}\;{NUM}_{i}} = {m.}$

When m=3, one 2³QAM symbol is mapped from three bits that are separately from Z code words separately denoted as A_(i), where 0<i≤Z, and a quantity of bits included in a code word A_(i) is denoted as NUM_(i). For the embodiment shown in FIG. 2D, if m=3, Z=2, NUM₁=1, and NUM₂=2, the embodiment of FIG. 2A can be obtained; if m=3, Z=2, NUM₁=2, and NUM₂=1, the embodiment of FIG. 2B can be obtained; or if m=3, Z=3, NUM₁=1, NUM₂=1, and NUM₃=1, the embodiment of FIG. 2C can be obtained.

When m=4 to 12 and Z has different values, there is a preferred manner in which parameter values of NUM_(i) are configured. In this configuration manner, x_(i)>x_(i+1).

For example, when m=4, the parameter values of NUM_(i) may be shown in FIG. 7A. Parameter values of NUM_(i) shown in each row in FIG. 7A may have another arrangement.

When m=5, the parameter values of NUM_(i) may be shown in FIG. 7B. Parameter values of NUM_(i) shown in each row in FIG. 7B may have another arrangement.

When m=6, the parameter values of NUM_(i) may be shown in FIG. 7C. Parameter values of NUM_(i) shown in each row in FIG. 7C may have another arrangement.

When m=7, the parameter values of NUM_(i) may be shown in FIG. 7D. Parameter values of NUM_(i) shown in each row in FIG. 7D may have another arrangement.

When m=8, the parameter values of NUM_(i) may be shown in FIG. 7E. Parameter values of NUM_(i) shown in each row in FIG. 7E may have another arrangement.

When m=9, the parameter values of NUM_(i) may be shown in FIG. 7F. Parameter values of NUM_(i) shown in each row in FIG. 7F may have another arrangement.

When m=10, the parameter values of NUM_(i) may be shown in FIG. 7G. Parameter values of NUM_(i) shown in each row in FIG. 7G may have another arrangement.

When m=11, the parameter values of NUM_(i) may be shown in FIG. 7H. Parameter values of NUM_(i) shown in each row in FIG. 7H may have another arrangement.

When m=12, the parameter values of NUM_(i) may be shown in FIG. 7I. Parameter values of NUM_(i) shown in each row in FIG. 7I may have another arrangement.

When m is greater than 12 and Z has different values, there may be a similar configuration manner, and details are not described herein.

In this embodiment of this application, for the 2^(m)QAM modulation, the mapped symbol is corresponding to one constellation point in 2^(m) constellation points in a 2^(m) constellation diagram, a minimum Euclidean distance between the constellation points in the 2^(m) constellation diagram is a first Euclidean distance. Preferably, a minimum Euclidean distance between constellation points that are in the 2^(m) constellation diagram and that may be corresponding to the first-type symbols after bits from the first code word are determined is a second Euclidean distance, and the second Euclidean distance is greater than the first Euclidean distance.

There are in total 2^(m) modulation symbols {s¹, s², . . . , s² ^(m) } in the 2^(m)QAM modulation scheme, which are corresponding to 2^(m) constellation points in the modulation constellation diagram. Each modulation symbol s^(j) is mapped from m bits (b¹, b², . . . b^(m)).

It is assumed that the m bits (b¹, b², . . . b^(m)) may be mapped into 2^(m) symbols that are denoted as a set S₀, and a minimum Euclidean distance between the symbols is W₀.

First Segmentation:

In the set, when b¹=b²= . . . =b^(NUM1)=0, corresponding symbols form a set S_(0,0) that is a subset of S₀, and a minimum distance between the symbols in the subset is W_(1,0). That is, b¹, b², . . . , b^(NUM1) are bits from the first code word. After it is determined that b¹=b²= . . . =b^(NUM1)=0, the minimum Euclidean distance between the possible constellation points is W_(1,0).

In the set, when b¹=b²= . . . =b^(NUM1)=1, corresponding symbols form a set S_(0,1) that is a subset of S₀, and a minimum distance between the symbols is W_(1,1), that is, b¹, b², . . . , b^(NUM1) are bits from the first code word. After it is determined that b¹=b²= . . . =b^(NUM1)=1 the minimum Euclidean distance between the possible constellation points may be W_(1,1).

In addition, W₁=min(W_(1,0), W_(1,1)), and preferably, W₁>W₀.

Further, Second Segmentation:

In the set, when b¹=b²= . . . =b^(NUM) ¹ =0 and b^(NUM) ¹ ⁺¹=b^(NUM) ¹ ⁺²= . . . =b^(NUM) ² =0, corresponding symbols form a set S_(1,0,0) that is a subset of S_(1,0), and a minimum distance between the symbols in the subset is W_(2,0,0).

In the set, when b¹=b²= . . . =b^(NUM) ¹ =0 and b^(NUM) ¹ ⁺¹=b^(NUM) ¹ ⁺²= . . . =b^(NUM) ² =1, corresponding symbols form a set S_(1,0,1) that is a subset of S_(1,0), and a minimum distance between the symbols in the subset is W_(2,0,1).

In the set, when b¹=b²= . . . =b^(NUM) ¹ =0 and b^(NUM) ¹ ⁺¹=b^(NUM) ¹ ⁺²= . . . =b^(NUM) ² =0, corresponding symbols form a set S_(1,0,0) that is a subset of S_(1,0), and a minimum distance between the symbols in the subset is W_(2,1,0).

In the set, when b¹=b²= . . . =b^(NUM) ¹ =0 and b^(NUM) ¹ ⁺¹=b^(NUM) ¹ ⁺²= . . . =b^(NUM) ² =1, corresponding symbols form a set S_(1,0,1) that is a subset of S_(1,0), and a minimum distance between the symbols in the subset is W_(2,1,1).

In addition, W₂=min(W_(2,0,0), W_(2,0,1), W_(2,1,0), W_(2,1,1)), and preferably, W₂>W₁.

. . . .

(z−1)^(th) segmentation:

After the set S₀ is segmented for z times, 2^(z) sets are generated, and each set is a part of S₀. After the (z−1)^(th) segmentation, a minimum Euclidean distance in the set is denoted as W_(z-1).

Preferably, W_(z)>W_(z-1).

The following uses the 8QAM modulation as an example for description. It is assumed that Z=2, NUM₁=1, and NUM₂=2, which is the case shown in FIG. 2A and FIG. 3A.

There are in total eight modulation symbols {s₁, . . . , s₆, s₈} in an 8QAM modulation scheme, which are corresponding to eight constellation points in the constellation diagram. Each modulation symbol s_(j) is mapped from three data bits (d₁,d₂,d₃).

Table 2 shows a method for mapping three bits into a complex number symbol s=I+jQ. A constellation diagram obtained by means of mapping according to Table 1 is shown in FIG. 4A.

TABLE 2 Constellation point mapping in 8QAM Bits I Q 000 −2 0 001 0 2 011 2 0 010 0 −2 110 3 −3 111 3 3 101 −3 3 100 −3 −3

It can be seen from the figure that, when a first bit is determined, constellation points that may be corresponding to the symbol may be considered as a QPSK constellation diagram. For example, when the first bit is 0, the constellation points that may be corresponding to the symbol are four constellation points shown in an inner circle. The four constellation points may be considered as a QPSK constellation diagram. When the first bit is 1, the constellation points that may be corresponding to the symbol are four constellation points shown in an outer circle. The four constellation points may also be considered as a QPSK constellation diagram. It is well known that a minimum Euclidean distance between QPSK constellation points is greater than a minimum Euclidean distance between 8QAM constellation points. When the first bit is known, it means that the Euclidean distance is enlarged.

Table 3 shows another method for mapping three bits into a complex number symbol s=I+jQ. A constellation diagram obtained by means of mapping according to Table 3 is shown in FIG. 4B.

TABLE 3 Constellation point mapping in 8QAM Bits I Q 000 3 −1 001 1 −3 010 3 3 011 −3 −3 100 1 1 101 −1 −1 110 −1 3 111 −3 1

It can be seen from FIG. 4B that, after a first bit is determined, constellation points that may be corresponding to the symbol may be considered as a QPSK constellation diagram. When the first bit is 0, the constellation points that may be corresponding to the symbol are a square constellation diagram (a solid line part) shown in an upper-right diagram. When the first bit is 1, the constellation points that may be corresponding to the symbol are a lower-right constellation diagram (a solid line part). A Euclidean distance between constellation points in two right constellation diagrams is greater than a Euclidean distance between eight points in a left diagram. When the first bit is known, it means that the Euclidean distance is enlarged.

As shown in FIG. 2E, FIG. 2E is a structural diagram of a transmit end device according to an embodiment of this application. A difference between FIG. 2E and FIG. 2A is that a modulator in FIG. 2E includes an interleaver 2034 and a mapper 2033, and does not include an interleaver 202.

The interleaver 2032 interleaves a received coded bit stream. For example, the received coded bit stream is Q={{q_(1,1), q_(1,2), . . . , q_(1,n)}, {q_(2,1), q_(2,2), . . . , q_(2,n)}, {q_(3,1),q_(3,2), . . . , q_(3,n)} . . . }, and it is assumed that n=12.

It is assumed that A={a₁, a₂, a₃, a₄, a₅, a₆, a₇, a₈, a₉, a₁₀, a₁₁, a₁₂, . . . }={{Q_(1,1), Q_(1,2), Q_(1,3), Q_(1,4), Q_(1,5), Q_(1,6), Q_(1,7), Q_(1,8), Q_(1,9), Q_(1,10), Q_(1,11), Q_(1,12)}, {Q_(2,1), Q_(2,2), Q_(2,3), Q_(2,4), Q_(2,5), Q_(2,6), Q_(2,7), Q_(2,8), Q_(2,9), Q_(2,10), Q_(2,11), Q_(2,12)}, . . . }, that is, {a₁, a₂, a₃, a₄, a₅, a₆, a₇, a₈, a₉, a₁₀, a₁₁, a₁₂} is corresponding to a code word Q1={Q_(1,1), Q_(1,2), Q_(1,3), Q_(1,4), Q_(1,5), Q_(1,6), Q_(1,7), Q_(1,8), Q_(1,9), Q_(1,10), Q_(1,11), Q_(1,12)}, and a bit a₁₃ to a bit a₂₄ are corresponding to a code word A2.

The following describes processing performed by the interleaver 2034 on a sequence A, and m sequences are output after the processing. The following describes two typical interleaving rules.

In Rule 1, the output m sequences are respectively:

$D_{1} = \left\{ {\overset{\overset{x_{1} \times \frac{n}{m}}{︷}}{X,X,X,\ldots\mspace{11mu},X},a_{1},a_{m + 1},a_{{2m} + 1},\ldots} \right\}$  ⋮ $D_{{NUM}_{1}} = \left\{ {\overset{\overset{x_{1} \times \frac{n}{m}}{︷}}{X,X,X,\ldots\mspace{11mu},X},a_{{NUM}_{1}},a_{m + {NUM}_{1}},a_{{2m} + {NUM}_{1}},\ldots} \right\}$ $D_{{NUM}_{1} + 1} = \left\{ {\overset{\overset{x_{2} \times \frac{n}{m}}{︷}}{X,{X\mspace{14mu}\ldots}\mspace{11mu},X},a_{{NUM}_{1} + 1},a_{m + {NUM}_{1} + 1},a_{{2m} + {NUM}_{1} + 1},\ldots} \right\}$  ⋮ $D_{{NUM}_{1} + {NUM}_{2}} = \left\{ {\overset{\overset{x_{2} \times \frac{n}{m}}{︷}}{X,{X\mspace{14mu}\ldots}\mspace{11mu},X},a_{{NUM}_{1} + {NUM}_{2}},a_{m + {NUM}_{1} + {NUM}_{2}},a_{{2m} + {NUM}_{1} + {NUM}_{2}},\ldots} \right\}$  ⋮ $D_{m - {NUM}_{Z} + 1} = \left\{ {\overset{\overset{x_{z} \times \frac{n}{m}}{︷}}{X,{\ldots\mspace{14mu} X}},a_{m - {NUM}_{Z} + 1},a_{{2m} - {NUM}_{Z} + 1},a_{{3m} - {NUM}_{Z} + 1},\ldots} \right\}$  ⋮ $D_{m} = \left\{ {\overset{\overset{x_{Z} \times \frac{n}{m}}{︷}}{X,{\ldots\mspace{14mu} X}},a_{m},a_{2m},a_{3m},\ldots} \right\}$

In this case, an interleaving rule of the interleaver includes: outputting the m sequences; and outputting an interleaved bit a_(L) in a (row=L % m)^(th) row and a (col=└L/m┘+1+DY_(L))^(th) column. L % m is a reminder of L/m, and └L/m┘ is an integer obtained after L/m is rounded off. It can be learned that when

${{row} = {{NUM}_{i - 1} + 1}},{{NUM}_{i - 1} + 2},\ldots\mspace{11mu},{NUM}_{i},{{DY}_{L} = {x_{i} \times {\left( \frac{n}{m} \right).}}}$

In this interleaving rule, if m=3, x₁=2, x₂=1, and x₃=0,

D1={X, X, X, X, X, X, X, X, a₁, a₄, a₇, a₁₀, a₁₃, a₁₆, a₁₉, a₂₂, . . . };

D2={X, X, X, X, a₂, a₅, a₈, a₁₁, a₁₄, a₁₇, a₂₀, a₂₃, . . . }; and

D3={a₃, a₆, a₉, a₁₂, a₁₅, a₁₈, a₂₁, a₂₄, . . . }.

That is,

D1={X, X, X, X, X, X, X, X, Q_(1,1), Q_(1,4), Q_(1,7), Q_(1,10), Q_(2,1), Q_(2,4), Q_(2,7), Q_(2,10), . . . };

D2={X, X, X, X, Q_(1,2), Q_(1,5), Q_(1,8), Q_(1,11), Q_(2,2), Q_(2,5), Q_(2,8), Q_(2,11), . . . }; and

D3={Q_(1,3), Q_(1,6), Q_(1,9), Q_(1,12), Q_(2,3), Q_(2,6), Q_(2,9), Q_(2,12), . . . }.

In Rule 2, the output m sequences are respectively:

$D_{1} = \left\{ {\overset{\overset{x_{1} \times \frac{n}{m}}{︷}}{X,X,X,\ldots\mspace{11mu},X},a_{1},a_{2},\ldots\mspace{11mu},{a_{n/m}\mspace{14mu}\ldots}} \right\}$  ⋮ $D_{{NUM}_{1}} = \left\{ {\overset{\overset{x_{1} \times \frac{n}{m}}{︷}}{X,X,X,\ldots\mspace{11mu},X},a_{{{({{NUM}_{1} - 1})} \times {n/m}} + 1},a_{{{({{NUM}_{1} - 1})} \times {n/m}} + 2},\ldots\mspace{11mu},a_{{NUM}_{1} \times {n/m}},\ldots} \right\}$ $D_{{NUM}_{1} + 1} = \left\{ {\overset{\overset{x_{2} \times \frac{n}{m}}{︷}}{X,{X\mspace{14mu}\ldots}\mspace{11mu},X},a_{{{NUM}_{1} \times {n/m}} + 1},a_{{{NUM}_{1} \times {n/m}} + 2},\ldots\mspace{11mu},a_{{({{NUM}_{1} + 1})} \times {n/m}},\ldots} \right\}$  ⋮ $D_{{NUM}_{1} + {NUM}_{2}} = \left\{ {\overset{\overset{x_{2} \times \frac{n}{m}}{︷}}{X,{X\mspace{14mu}\ldots}\mspace{11mu},X},a_{{{({{NUM}_{1} + {NUM}_{2} - 1})} \times {n/m}} + 1},a_{{{({{NUM}_{1} + {NUM}_{2} - 1})} \times {n/m}} + 2},\ldots\mspace{11mu},a_{{({{NUM}_{1} + {NUM}_{2}})} \times {n/m}},\ldots} \right\}$ ⋮ $D_{m - {NUM}_{Z} + 1} = \left\{ {\overset{\overset{x_{Z} \times \frac{n}{m}}{︷}}{X,{\ldots\mspace{14mu} X}},a_{{{({m - {NUM}_{Z}})} \times {n/m}} + 1},a_{{{({m - {NUM}_{Z}})} \times {n/m}} + 2},\ldots\mspace{11mu},a_{{({m - {NUM}_{Z} + 1})} \times {n/m}},\ldots} \right\}$  ⋮ $D_{m} = \left\{ {\overset{\overset{x_{Z} \times \frac{n}{m}}{︷}}{X,{\ldots\mspace{14mu} X}},a_{{{({m - 1})} \times {n/m}} + 1},a_{{{({m - 1})} \times {n/m}} + 2},\ldots\mspace{11mu},a_{m \times {n/m}},\ldots} \right\}$

In this case, an interleaving rule of the interleaver includes: outputting the m sequences; and outputting an interleaved bit a_(L) in a (row=(L−└L/n┘×n)/(n/m)+1)^(th) row and a (col=└L/n┘×(n/m)+L % (n/m)+DY_(L))^(th) column. L % (n/m) is a reminder of L/(n/m), and └L/m┘ is an integer obtained after L/m is rounded off. It can be learned that when

${{row} = {{NUM}_{i - 1} + 1}},{{NUM}_{i - 1} + 2},\ldots\mspace{11mu},{NUM}_{i},{{DY}_{L} = {x_{i} \times {\left( \frac{n}{m} \right).}}}$

In this interleaving rule, if m=3, x₁=2, x₂=1, and x₃=0,

D1={X, X, X, X, X, X, X, X, a₁, a₂, a₃, a₄, a₁₃, a₁₄, a₁₅, a₁₆, . . . };

D2={X, X, X, X, a₅, a₆, a₇, a₈, a₁₇, a₁₈, a₁₉, a₂₀, . . . }; and

D3={a₉, a₁₀, a₁₁, a₁₂, a₂₁, a₂₂, a₂₃, a₂₄, . . . }.

That is,

D1={X, X, X, X, X, X, X, X, Q_(1,1), Q_(1,2), Q_(1,3), Q_(1,4), Q_(2,1), Q_(2,2), Q_(2,3), Q_(2,4), . . . };

D2={X, X, X, X, Q_(1,5), Q_(1,6), Q_(1,7), Q_(1,8), Q_(2,5), Q_(2,6), Q_(2,7), Q_(2,8), . . . }; and

D3={Q_(1,9), Q_(1,10), Q_(1,11), Q_(1,12), Q_(2,9), Q_(2,10), Q_(2,11), Q_(2,12), . . . }.

In an actual application, there may be a plurality of interleaving rules, provided that each sequence in M sequences includes N/M bits from the first code word, and a symbol finally obtained by means of mapping meets that first bits corresponding to N/M first-type symbols are from the first code word, and second bits corresponding to N/M second-type symbols are from the first code word. Bits may be interleaved in a disrupted order, and bits of two code words may also be interleaved in a disrupted order.

In this embodiment of this application, a code word sequence is mapped into M sequences, each sequence includes N/M bits from the first code word; the M sequences are mapped into a symbol sequence, where each symbol is corresponding to M bits, the M bits are respectively from the M sequences, the first bits corresponding to the N/M first-type symbols are from the first code word, and the second bits corresponding to the N/M second-type symbols are from the first code word. That is, locations of bits related to the first code word in the M sequences are staggered. Some bits in the M bits corresponding to the first-type symbol are from the first code word, and some bits are from another code word. Some bits in the M bits corresponding to the second-type symbol are from the first code word, and some bits are from another code word.

After receiving the first-type symbol, a receive end may demodulate the first-type symbol and the second-type symbol for a first time. After the bits related to the first code word are decoded, the first-type symbol or the second-type symbol may be demodulated again. Because the bits in the first-type symbol and from the first code word are already determined, bits in the first-type symbol and from another code word can be demodulated more accurately.

As shown in FIG. 5A, FIG. 5A is a structural diagram of a receive end device according to an embodiment of this application. The receive end device includes a demodulator 501 and a decoder 502.

The demodulator 501 is configured to: receive a symbol sequence transmitted by using a channel, where the symbol sequence is a symbol sequence generated in any one of claims 1 to 8; demodulate a first-type symbol to obtain a log-likelihood ratio of a bit from a first code word; and demodulate a second-type symbol to obtain a log-likelihood ratio of a bit from the first code word.

The decoder 502 is configured to perform decoding on log-likelihood ratios of all bits from the first code word to obtain first extrinsic information.

The demodulator 501 is further configured to receive the symbol sequence transmitted by using the channel, and demodulate the second-type symbol by using the first extrinsic information to obtain a log-likelihood ratio of a bit from another code word.

If the first-type symbol further includes a bit from a second code word,

the decoder 502 may further be configured to perform decoding on log-likelihood ratios of all bits from the second code word to obtain second extrinsic information; and

that the demodulator 501 is configured to demodulate the first-type symbol to obtain the log-likelihood ratio of the bit from the first code word includes:

the demodulator 501 is configured to demodulate the first-type symbol by using the second extrinsic information to obtain the log-likelihood ratio of the bit from first code word.

The receive end device may perform receiving by using a plurality of solutions, provided that the bits in the second-type symbol and from another code word are demodulated by using information about the first code word. The following provides a specific implementation apparatus and an implementation solution.

As shown in FIG. 5B, FIG. 5B is a structural diagram of another receive end device according to an embodiment of this application. The receive end device includes: a demodulator 501, a parallel-to-serial converter 503, a de-interleaver 504, a decoder 502, and an interleaver 505. The demodulator 501 specifically includes a demodulation submodule 5011, a cache 5012, a demodulation submodule 5013, and a selector 5014.

8QAM is used as an example to describe a receiving method of the receive end device in FIG. 5B. According to the foregoing description of the transmit end in the embodiments related to FIG. 2A and FIG. 3A, each modulation symbol s^(j) of the 8QAM is mapped from three data bits (d₁,d₂,d₃), where d₁ is from a previous code word, and d₂ and d₃ are from a second code word.

It is assumed that a coded code word is modulated to obtain a modulation symbol s, and a receiving symbol obtained after s passes through a channel is: y=s+n  (1)

where, n is an additive noise of the channel, and dimensions of the additive noise accord with complex Gaussian distribution whose mean value is 0 and whose variance is σ².

It is assumed that a receiving symbol y_(f) is mapped from three bits and is denoted as {d₁,d₂,d₃}, the bit d₁ is from a code word A_(i), and d₂,d₃ are from a code word A_(i+1).

FIG. 6A and FIG. 6B are a processing flowchart of a receive end device according to an embodiment of this application. Specifically:

For f=1 to n/3, which is corresponding to FIG. 3A:

(1) A demodulation submodule 5011 performs first demodulation on the receiving symbol y_(f) to obtain log-likelihood ratios of bits that are from a code word A₁ and that are mapped into sequences D2 and D3, and the log-likelihood ratios of the bits are cached until a remaining bit of the code word A₁ is demodulated.

For f=1+3/n to 2*n/3:

(2) The demodulation submodule 5011 performs first demodulation on the receiving symbol y_(f) to obtain a log-likelihood ratio of a bit that is from the code word A₁ and that is mapped into a sequence D1, and the cache 5012 caches information about the symbol y_(f). So far, all bits of the code word A₁ are demodulated.

(3) After a parallel-to-serial converter 503 performs parallel-to-serial conversion on the log-likelihood ratios of the bits obtained after demodulation to obtain one piece of information, a de-interleaver 504 performs de-interleaving on the information. A de-interleaving rule is a reverse process of interleaving performed by a transmit end.

(4) De-interleaved log-likelihood ratios of the bits are sent to a decoder 502 for decoding, so as to obtain hard decision information and extrinsic information. The hard decision information is final information obtained by the receive end by means of decoding.

(5) An interleaver 505 re-interleaves the extrinsic information obtained by means of decoding, and an interleaving process is the same as the interleaving process on the transmit end.

(6) A demodulation submodule 5013 performs, by using the extrinsic information obtained in step (4), second demodulation on bits that are in y_(f) (f=3/n to 2*n/3) and that are from a code word A₂, so as to obtain log-likelihood ratios of bits that are from the code word A₂ and that are mapped into sequences D2 and D3, and the log-likelihood ratios of the bits are cached until a remaining bit of the code word A₂ is demodulated.

For f=1+2*n/3 to n:

(7) The demodulation submodule 5011 performs first demodulation on the receiving symbol y_(f) to obtain a log-likelihood ratio of a bit that is from the code word A₂ and that is mapped into the sequence D1, and the cache 5012 caches information about the symbol y_(f). So far, all bits of the code word A₂ are demodulated.

(8) Step (3) to step (6) are performed to obtain hard decision information and extrinsic information of the code word A₂, and the extrinsic information is used to obtain log-likelihood ratios of bits that are in the receiving symbol y_(f) (f=2*n/3 to n), that are from a code word A₃, and that are mapped into the sequences D2 and D3.

When f is another value, step (7) and step (8) are repeated to demodulate and decode a receiving symbol.

The following describes the first demodulation performed by the demodulation submodule 5011.

Euclidean distances between the receiving symbol and each constellation point are calculated. An LLR of a bit di is a value obtained by subtracting a sum of Euclidean distances between the symbol and constellation points when di=0 from a sum of Euclidean distances between the symbol and constellation points when di=1. This may be further simplified as follows: The LLR of the bit di is a value obtained by subtracting a minimum value in the Euclidean distances between the symbol and the constellation points when di=0 from a minimum value in the Euclidean distances between the symbol and the constellation points when di=1.

Specifically, formulas (1) to (4) may be used for description.

A symbol probability that a sending symbol s_(i) obtained based on a receiving symbol is s^(j) is:

$\begin{matrix} {{p\left( {s_{i} = \left. s^{j} \middle| y_{i} \right.} \right)} = {\frac{1}{\sqrt{2\;{\pi\sigma}^{2}}}{\exp\left( {- \frac{{{y_{i} - s^{i}}}^{2}}{2\sigma^{2}}} \right)}}} & (1) \end{matrix}$

where, y_(i) is a symbol received by a receiving system at a moment i, and s_(i) is a symbol that is sent by a transmit end and that is corresponding to y_(i).

p(s_(i)=s^(j)/y_(i)) represents a probability that when the receiving symbol y_(i) is known, the symbol s_(i) sent by the transmit end is s^(j). σ is a standard deviation of a Gaussian channel, and exp is an index operation.

A log-likelihood ratio of each bit is:

$\begin{matrix} \begin{matrix} {\mspace{79mu}{{{LLR}\left( d_{k} \right)} = {\ln\left( \frac{p\left( {d_{k} = \left. 0 \middle| y_{i} \right.} \right)}{p\left( {d_{k} = \left. 1 \middle| y_{i} \right.} \right)} \right)}}} \\ {= {\ln\left( \frac{\sum\limits_{j = 1}^{M}\;{{I\left( {d_{k} = \left. 0 \middle| s^{j} \right.} \right)}{\exp\left( {- \frac{{{y_{i} - s^{j}}}^{2}}{2\sigma^{2}}} \right)}}}{\sum\limits_{j = 1}^{M}\;{{I\left( {d_{k} = \left. 1 \middle| s^{j} \right.} \right)}{\exp\left( {- \frac{{{y_{i} - s^{j}}}^{2}}{2\sigma^{2}}} \right)}}} \right)}} \end{matrix} & (2) \\ {{I\left( {d_{k} = \left. a \middle| s^{j} \right.} \right)} = \left\{ \begin{matrix} {1\mspace{14mu} A\mspace{14mu} k^{th}\mspace{14mu}{bit}\mspace{14mu} d_{k}\mspace{14mu}{corresponding}\mspace{14mu}{to}\mspace{14mu} a\mspace{14mu}{symbol}\mspace{14mu} s^{j}\mspace{14mu}{is}\mspace{14mu}{equal}\mspace{14mu}{to}\mspace{14mu} a} \\ {0\mspace{14mu} A\mspace{14mu} k^{th}\mspace{14mu}{bit}\mspace{14mu} d_{k}\mspace{14mu}{corresponding}\mspace{14mu}{to}\mspace{14mu} a\mspace{14mu}{symbol}\mspace{14mu} s^{j}\mspace{14mu}{is}\mspace{14mu}{not}\mspace{14mu}{equal}\mspace{14mu}{to}\mspace{14mu} a} \end{matrix} \right.} & (3) \end{matrix}$

where, y_(i) is a symbol received by a receiving system at a moment i, and s_(i) is a symbol that is sent by a transmit end and that is corresponding to y_(i). LLR(d_(k)) is a log-likelihood ratio of a k^(th) bit, and ln is a natural logarithm.

p(d_(k)=0|y_(i)) represents a probability that when the receiving symbol y_(i) is known, the k^(th) bit of the symbol s_(i) sent by the transmit end is 0. p(d_(k)=1|y_(i)) represents a probability that when the receiving symbol y_(i) is known, the k^(th) bit of the symbol s_(i) sent by the transmit end is 1. σ is a standard deviation of a Gaussian channel, and exp represents an index operation.

In an actual application, only maximum values in sum terms may be obtained, and in this case, the log-likelihood ratio of each code word bit may be simplified as follows:

$\begin{matrix} {{{LLR}\left( d_{k} \right)} \approx {\ln\left( \frac{\max\limits_{{j = 1},2,\ldots,M}\left\{ {{I\left( {d_{k} = \left. 0 \middle| s^{j} \right.} \right)}{\exp\left( {- \frac{{{y_{i} - s^{j}}}^{2}}{2\sigma^{2}}} \right)}} \right\}}{\max\limits_{{j = 1},2,\ldots,M}\left\{ {{I\left( {d_{k} = \left. 1 \middle| s^{j} \right.} \right)}{\exp\left( {- \frac{{{y_{i} - s^{j}}}^{2}}{2\sigma^{2}}} \right)}} \right\}} \right)}} & (4) \end{matrix}$

where, y_(i) is a symbol received by a receiving system at a moment i, and s_(i) is a symbol that is sent by a transmit end and that is corresponding to y_(i). LLR(d_(k)) is a log-likelihood ratio of a k^(th) bit, and ln is a natural logarithm.

p(d_(k)=0|y_(i)) represents a probability that when the receiving symbol y_(i) is known, the k^(th) bit of the symbol s_(i) sent by the transmit end is 0. P(d_(k)=1|y_(i)) represents a probability that when the receiving symbol y_(i) is known, the k^(th) bit of the symbol s_(i) sent by the transmit end is 1. σ is a standard deviation of a Gaussian channel, and exp represents an index operation.

The following describes the second demodulation performed by the demodulation submodule 5013.

(1) Euclidean distances between the receiving symbol and each constellation point are calculated. Euclidean distances between the receiving symbol and constellation points when d=0 are updated to original Euclidean distances superposed with the extrinsic information output by the decoder. Euclidean distances between the receiving symbol and constellation points when di=1 remain unchanged.

(2) An LLR of a bit d_(k) is a value obtained by subtracting a sum of Euclidean distances between the symbol and constellation points when d_(k)=0 from a sum of Euclidean distances between the symbol and constellation points when d_(k)=1. This may be further simplified as follows: The LLR of the bit d_(k) is a value obtained by subtracting a minimum value in the Euclidean distances between the symbol and the constellation points when d_(k)=0 from a minimum value in the Euclidean distances between the symbol and the constellation points when d_(k)=1.

Specifically, a formula (5) may be used.

A calculation manner of a symbol probability of the symbol when d₁=0 is updated to:

$\begin{matrix} \begin{matrix} {{p\left( {s = \left. s^{j} \middle| y_{i} \right.} \right)} = {\frac{1}{\sqrt{2{\pi\sigma}^{2}}}{\exp\left( {- \frac{{{y_{i} - s^{j}}}^{2}}{2\sigma^{2}}} \right)} \times \exp^{{Ex}{(d_{0,{i - 1}})}}}} \\ {= {\frac{1}{\sqrt{2{\pi\sigma}^{2}}}{\exp\left( {{- \frac{{{y_{i} - s^{j}}}^{2}}{2\sigma^{2}}} + {{Ex}\left( d_{0,{i - 1}} \right)}} \right)}}} \end{matrix} & (5) \end{matrix}$

A calculation manner of a symbol probability of the symbol when d_(i)=1 is still the formula (1).

Then, log-likelihood ratios of each d₂,d₃ are calculated based on the first demodulation (refer to formulas (2), (3), and (4)), where

y_(i) is a symbol received by a receiving system at a moment i, and s_(i) is a symbol that is sent by a transmit end and that is corresponding to y_(i). p(s_(i)=s^(j)|y_(i)) represents a probability that when the receiving symbol y_(i) is known, the symbol s_(i) sent by the transmit end is s^(j). σ is a standard deviation of a Gaussian channel, and exp represents an index operation.

In an embodiment, a value of the extrinsic information mentioned above may be obtained in three manners, respectively:

(1) The extrinsic information is information obtained after prior information input to the decoder is subtracted from posterior information obtained by the decoder.

(2) The extrinsic information is posterior information obtained by the decoder.

(3) A symbol in the value of (1) or (2) remains unchanged. If decoding is correct, the value is set to infinity; or, if decoding is incorrect, the value is set to 0.

Persons skilled in the art should understand that the embodiments of this application may be provided as a method, or a computer program product. Therefore, this application may use a form of hardware only embodiments, software only embodiments, or embodiments with a combination of software and hardware. Moreover, this application may use a form of a computer program product that is implemented on one or more computer-usable storage media (including but not limited to a disk memory, a CD-ROM, an optical memory, and the like) that include computer usable program code.

This application is described with reference to the flowcharts and/or block diagrams of the method, the device (system), and the computer program product according to the embodiments of this application. It should be understood that computer program instructions may be used to implement each process and/or each block in the flowcharts and/or the block diagrams and a combination of a process and/or a block in the flowcharts and/or the block diagrams. These computer program instructions may be provided for a general-purpose computer, a dedicated computer, an embedded processor, or a processor of any other programmable data processing apparatus to generate a machine, so that the instructions executed by a computer or a processor of any other programmable data processing apparatus generate an apparatus for implementing a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.

These computer program instructions may be stored in a computer readable memory that can instruct the computer or any other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer readable memory generate an artifact that includes an instruction apparatus. The instruction apparatus implements a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.

These computer program instructions may also be loaded onto a computer or another programmable data processing apparatus, so that a series of operations and steps are performed on the computer or the another programmable apparatus, thereby generating computer-implemented processing. Therefore, the instructions executed on the computer or the another programmable apparatus provide steps for implementing a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.

Although some preferred embodiments of this application have been described, persons skilled in the art can make changes and modifications to these embodiments once they learn the basic inventive concept. Therefore, the following claims are intended to be construed as to cover the preferred embodiments and all changes and modifications falling within the scope of this application.

Obviously, persons skilled in the art can make various modifications and variations to this application without departing from the scope of this application. This application is intended to cover these modifications and variations of this application provided that they fall within the scope of protection defined by the following claims and their equivalent technologies. 

What is claimed is:
 1. A modulation method, comprising: receiving, by a transmitter device in a communication system, a code word sequence, wherein each code word in the code sequence comprises N bits, and the code word sequence comprises a first code word; mapping, by the transmitter device, the code word sequence into M sequences, wherein each sequence of the M sequences comprises N/M bits from the first code word; mapping, by the transmitter device, the M sequences into a symbol sequence, wherein each symbol in the symbol sequence corresponds to M bits, the M bits are respectively from the M sequences, a first set of bits corresponding to N/M first-type symbols are from the first code word, and a second set of bits corresponding to N/M second-type symbols are from the first code word; and transmitting, by the transmitter device, the symbol sequence to a receiver device in the communication system.
 2. The method according to claim 1, wherein each symbol in the symbol sequence corresponds to one constellation point in 2^(M) constellation points in a 2^(M) constellation diagram, a minimum Euclidean distance between the constellation points in the 2^(M) constellation diagram is a first Euclidean distance, a minimum Euclidean distance between constellation points that are in the 2^(M) constellation diagram and that correspond to the first-type symbols after bits from the first code word are determined is a second Euclidean distance, and the second Euclidean distance is greater than the first Euclidean distance.
 3. The method according to claim 1, wherein the mapping the code word sequence into M sequences comprises: performing serial-to-parallel conversion on the code word sequence to obtain the M sequences; and performing delay processing on at least one sequence in the M sequences, wherein a quantity of delayed bits is X*(N/M), and X is an integer greater than or equal to
 1. 4. The method according to claim 1, wherein the mapping the code word sequence into M sequences comprises: interleaving the code word sequence to obtain the M sequences.
 5. The method according to claim 1, wherein when M is 3, and the mapping the code word sequence into M sequences comprises: performing serial-to-parallel conversion on the code word sequence to obtain three sequences, wherein each sequence comprises N/3 bits from the first code word; and performing delay processing on a first sequence of the M sequences, wherein a quantity of delayed bits is N/3.
 6. The method according to claim 1, wherein when M is 3, and the mapping the code word sequence into M sequences comprises: performing serial-to-parallel conversion on the code word sequence to obtain three sequences, wherein each sequence of the M sequences comprises N/3 bits from the first code word; performing delay processing on a first sequence of the M sequences, wherein a quantity of delayed bits is N/3; and performing delay processing on a second sequence of the M sequences, wherein a quantity of delayed bits is N/3.
 7. The method according to claim 1, wherein when M is 3, and the mapping the code word sequence into M sequences comprises: performing serial-to-parallel conversion on the code word sequence to obtain three sequences, wherein each sequence of the M sequences comprises N/3 bits from the first code word; performing delay processing on a first sequence of the M sequences, wherein a quantity of delayed bits is 2(N/3); and performing delay processing on a second sequence of the M sequences, wherein a quantity of delayed bits is N/3.
 8. A receiving method, comprising: receiving, by a receiver device from a transmitter device in a communications system, a symbol sequence transmitted using a channel; demodulating, by the receiver device, a first-type symbol from the symbol sequence to obtain a log-likelihood ratio of a bit from a first code word; demodulating, by the receiver device, a second-type symbol from the symbol sequence to obtain a log-likelihood ratio of a bit from the first code word; performing, by the receiver device, decoding based on log-likelihood ratios of bits from the first code word to obtain first extrinsic information; and demodulating, by the receiver device, the second-type symbol using the first extrinsic information to obtain a log-likelihood ratio of a bit from another code word.
 9. The method according to claim 8, wherein the first-type symbol further comprises a bit from a second code word, and before the demodulating the first-type symbol to obtain the log-likelihood ratio of the bit from the first code word, the method further comprises: performing decoding based on log-likelihood ratios of bits from the second code word to obtain second extrinsic information; wherein the demodulating the first-type symbol to obtain the log-likelihood ratio of the bit from the first code word comprises: demodulating the first-type symbol using the second extrinsic information to obtain the log-likelihood ratio of the bit from first code word.
 10. The method according to claim 8, wherein the first extrinsic information is information obtained after prior information of the decoding is subtracted from later information that is obtained after the decoding.
 11. A modulation apparatus, comprising: a memory storing instructions; and a processor configured to execute the instructions to cause the modulation apparatus to: receive a code word sequence, wherein each code word in the code word sequence comprises N bits, and the code word sequence comprises a first code word; map the code word sequence into M sequences, wherein each sequence of the M sequences comprises N/M bits from the first code word; and map the M sequences into a symbol sequence, wherein each symbol in the symbol sequence corresponds to M bits, the M bits are respectively from the M sequences, a first set bits of corresponding to N/M first-type symbols are from the first code word, and a second set of bits corresponding to N/M second-type symbols are from the first code word.
 12. The apparatus according to claim 11, wherein each symbol in the symbol sequence corresponds to one constellation point in 2^(M) constellation points in a 2^(M) constellation diagram, a minimum Euclidean distance between the constellation points in the 2^(M) constellation diagram is a first Euclidean distance, a minimum Euclidean distance between constellation points that are in the 2^(M) constellation diagram and that corresponds to the first-type symbols after bits from the first code word are determined is a second Euclidean distance, and the second Euclidean distance is greater than the first Euclidean distance.
 13. The apparatus according to claim 11, wherein executing the instructions further causes the modulation apparatus to: perform serial-to-parallel conversion on the code word sequence to obtain M sequences; and perform delay processing on at least one sequence in the M sequences, wherein a quantity of delayed bits is X*(N/M), and X is an integer greater than or equal to
 1. 14. The apparatus according to claim 11, wherein executing the instructions further causes the modulation apparatus to: interleave the code word sequence to obtain M sequences.
 15. The apparatus according to claim 11, wherein executing the instructions further causes the modulation apparatus to: perform serial-to-parallel conversion on the code word sequence to obtain three sequences, wherein each sequence comprises N/3 bits from the first code word; and perform delay processing on a first sequence of the M sequences, wherein a quantity of delayed bits is N/3.
 16. The apparatus according to claim 11, wherein executing the instructions further causes the modulation apparatus to: perform serial-to-parallel conversion on the code word sequence to obtain three sequences, wherein each sequence of the M sequences comprises N/3 bits from the first code word; perform delay processing on a first sequence of the M sequences, wherein a quantity of delayed bits is N/3; and perform delay processing on a second sequence of the M sequences, wherein a quantity of delayed bits is N/3.
 17. The apparatus according to claim 11, wherein executing the instructions further causes the modulation apparatus to: perform serial-to-parallel conversion on the code word sequence to obtain three sequences, wherein each sequence of the M sequences comprises N/3 bits from the first code word; perform delay processing on a first sequence of the M sequences, wherein a quantity of delayed bits is 2(N/3); and perform delay processing on a second sequence of the M sequences, wherein a quantity of delayed bits is N/3.
 18. A receiving apparatus, comprising: a memory storing instructions; and a processor configured to execute the instructions to cause the modulation apparatus to: receive a symbol sequence transmitted using a channel; demodulate a first-type symbol from the symbol sequence to obtain a log-likelihood ratio of a bit from a first code word; demodulate a second-type symbol from the symbol sequence to obtain a log-likelihood ratio of a bit from the first code word; perform decoding based on log-likelihood ratios of bits from the first code word to obtain first extrinsic information; receive the symbol sequence transmitted using the channel; and demodulate the second-type symbol using the first extrinsic information to obtain a log-likelihood ratio of a bit from another code word.
 19. The apparatus according to claim 18, wherein the first-type symbol further comprises a bit from a second code word, and wherein executing the instructions further causes the modulation apparatus to: perform decoding based on log-likelihood ratios of bits from the second code word to obtain second extrinsic information; wherein demodulating the first-type symbol to obtain the log-likelihood ratio of the bit from the first code word comprises: demodulating the first-type symbol using the second extrinsic information to obtain the log-likelihood ratio of the bit from first code word.
 20. The apparatus according to claim 18, wherein the first extrinsic information is information obtained after prior information of the decoding is subtracted from later information that is obtained after the decoding. 